why this coin was declarated on numista like non - circulated coin?
500 Fils - Isa (Isa Town) - Bahrain – Numista (https://en.numista.com/catalogue/pieces17146.html)
Is this circulated commemorative coin?
Maybe someone better know.
If you look at the standard circulation coins from that era you will find Bahrain made millions. Only 50 thousand of this coin were made, and there were no circulation coins of the same denomination, so there weren't enough for them to be a standard part of commerce. So it seems obvious they weren't intended to circulate.
There were also banknotes of the same denomination (1/2 Dinar) and rarely do countries have circulating coins and banknotes of the same value.